1 files changed, 78 insertions, 221 deletions

diff --git a/contrib/llvm/lib/Analysis/ScalarEvolutionNormalization.cpp b/contrib/llvm/lib/Analysis/ScalarEvolutionNormalization.cpp
index c1f9503816ee..2aaa4c1ae117 100644
--- a/contrib/llvm/lib/Analysis/ScalarEvolutionNormalization.cpp
+++ b/contrib/llvm/lib/Analysis/ScalarEvolutionNormalization.cpp
@@ -12,243 +12,100 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "llvm/IR/Dominators.h"
 #include "llvm/Analysis/LoopInfo.h"
 #include "llvm/Analysis/ScalarEvolutionExpressions.h"
 #include "llvm/Analysis/ScalarEvolutionNormalization.h"
 using namespace llvm;
 
-/// IVUseShouldUsePostIncValue - We have discovered a "User" of an IV expression
-/// and now we need to decide whether the user should use the preinc or post-inc
-/// value.  If this user should use the post-inc version of the IV, return true.
-///
-/// Choosing wrong here can break dominance properties (if we choose to use the
-/// post-inc value when we cannot) or it can end up adding extra live-ranges to
-/// the loop, resulting in reg-reg copies (if we use the pre-inc value when we
-/// should use the post-inc value).
-static bool IVUseShouldUsePostIncValue(Instruction *User, Value *Operand,
-                                       const Loop *L, DominatorTree *DT) {
-  // If the user is in the loop, use the preinc value.
-  if (L->contains(User)) return false;
-
-  BasicBlock *LatchBlock = L->getLoopLatch();
-  if (!LatchBlock)
-    return false;
-
-  // Ok, the user is outside of the loop.  If it is dominated by the latch
-  // block, use the post-inc value.
-  if (DT->dominates(LatchBlock, User->getParent()))
-    return true;
-
-  // There is one case we have to be careful of: PHI nodes.  These little guys
-  // can live in blocks that are not dominated by the latch block, but (since
-  // their uses occur in the predecessor block, not the block the PHI lives in)
-  // should still use the post-inc value.  Check for this case now.
-  PHINode *PN = dyn_cast<PHINode>(User);
-  if (!PN || !Operand) return false; // not a phi, not dominated by latch block.
-
-  // Look at all of the uses of Operand by the PHI node.  If any use corresponds
-  // to a block that is not dominated by the latch block, give up and use the
-  // preincremented value.
-  for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
-    if (PN->getIncomingValue(i) == Operand &&
-        !DT->dominates(LatchBlock, PN->getIncomingBlock(i)))
-      return false;
-
-  // Okay, all uses of Operand by PN are in predecessor blocks that really are
-  // dominated by the latch block.  Use the post-incremented value.
-  return true;
-}
+/// TransformKind - Different types of transformations that
+/// TransformForPostIncUse can do.
+enum TransformKind {
+  /// Normalize - Normalize according to the given loops.
+  Normalize,
+  /// Denormalize - Perform the inverse transform on the expression with the
+  /// given loop set.
+  Denormalize
+};
 
 namespace {
-
-/// Hold the state used during post-inc expression transformation, including a
-/// map of transformed expressions.
-class PostIncTransform {
-  TransformKind Kind;
-  PostIncLoopSet &Loops;
-  ScalarEvolution &SE;
-  DominatorTree &DT;
-
-  DenseMap<const SCEV*, const SCEV*> Transformed;
-
-public:
-  PostIncTransform(TransformKind kind, PostIncLoopSet &loops,
-                   ScalarEvolution &se, DominatorTree &dt):
-    Kind(kind), Loops(loops), SE(se), DT(dt) {}
-
-  const SCEV *TransformSubExpr(const SCEV *S, Instruction *User,
-                               Value *OperandValToReplace);
-
-protected:
-  const SCEV *TransformImpl(const SCEV *S, Instruction *User,
-                            Value *OperandValToReplace);
+struct NormalizeDenormalizeRewriter
+    : public SCEVRewriteVisitor<NormalizeDenormalizeRewriter> {
+  const TransformKind Kind;
+
+  // NB! Pred is a function_ref.  Storing it here is okay only because
+  // we're careful about the lifetime of NormalizeDenormalizeRewriter.
+  const NormalizePredTy Pred;
+
+  NormalizeDenormalizeRewriter(TransformKind Kind, NormalizePredTy Pred,
+                               ScalarEvolution &SE)
+      : SCEVRewriteVisitor<NormalizeDenormalizeRewriter>(SE), Kind(Kind),
+        Pred(Pred) {}
+  const SCEV *visitAddRecExpr(const SCEVAddRecExpr *Expr);
 };
-
 } // namespace
 
-/// Implement post-inc transformation for all valid expression types.
-const SCEV *PostIncTransform::
-TransformImpl(const SCEV *S, Instruction *User, Value *OperandValToReplace) {
-
-  if (const SCEVCastExpr *X = dyn_cast<SCEVCastExpr>(S)) {
-    const SCEV *O = X->getOperand();
-    const SCEV *N = TransformSubExpr(O, User, OperandValToReplace);
-    if (O != N)
-      switch (S->getSCEVType()) {
-      case scZeroExtend: return SE.getZeroExtendExpr(N, S->getType());
-      case scSignExtend: return SE.getSignExtendExpr(N, S->getType());
-      case scTruncate: return SE.getTruncateExpr(N, S->getType());
-      default: llvm_unreachable("Unexpected SCEVCastExpr kind!");
-      }
-    return S;
-  }
-
-  if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
-    // An addrec. This is the interesting part.
-    SmallVector<const SCEV *, 8> Operands;
-    const Loop *L = AR->getLoop();
-    // The addrec conceptually uses its operands at loop entry.
-    Instruction *LUser = &L->getHeader()->front();
-    // Transform each operand.
-    for (SCEVNAryExpr::op_iterator I = AR->op_begin(), E = AR->op_end();
-         I != E; ++I) {
-      Operands.push_back(TransformSubExpr(*I, LUser, nullptr));
+const SCEV *
+NormalizeDenormalizeRewriter::visitAddRecExpr(const SCEVAddRecExpr *AR) {
+  SmallVector<const SCEV *, 8> Operands;
+
+  transform(AR->operands(), std::back_inserter(Operands),
+            [&](const SCEV *Op) { return visit(Op); });
+
+  // Conservatively use AnyWrap until/unless we need FlagNW.
+  const SCEV *Result =
+      SE.getAddRecExpr(Operands, AR->getLoop(), SCEV::FlagAnyWrap);
+  switch (Kind) {
+  case Normalize:
+    // We want to normalize step expression, because otherwise we might not be
+    // able to denormalize to the original expression.
+    //
+    // Here is an example what will happen if we don't normalize step:
+    //  ORIGINAL ISE:
+    //    {(100 /u {1,+,1}<%bb16>),+,(100 /u {1,+,1}<%bb16>)}<%bb25>
+    //  NORMALIZED ISE:
+    //    {((-1 * (100 /u {1,+,1}<%bb16>)) + (100 /u {0,+,1}<%bb16>)),+,
+    //     (100 /u {0,+,1}<%bb16>)}<%bb25>
+    //  DENORMALIZED BACK ISE:
+    //    {((2 * (100 /u {1,+,1}<%bb16>)) + (-1 * (100 /u {2,+,1}<%bb16>))),+,
+    //     (100 /u {1,+,1}<%bb16>)}<%bb25>
+    //  Note that the initial value changes after normalization +
+    //  denormalization, which isn't correct.
+    if (Pred(AR)) {
+      const SCEV *TransformedStep = visit(AR->getStepRecurrence(SE));
+      Result = SE.getMinusSCEV(Result, TransformedStep);
     }
-    // Conservatively use AnyWrap until/unless we need FlagNW.
-    const SCEV *Result = SE.getAddRecExpr(Operands, L, SCEV::FlagAnyWrap);
-    switch (Kind) {
-    case NormalizeAutodetect:
-      // Normalize this SCEV by subtracting the expression for the final step.
-      // We only allow affine AddRecs to be normalized, otherwise we would not
-      // be able to correctly denormalize.
-      // e.g. {1,+,3,+,2} == {-2,+,1,+,2} + {3,+,2}
-      // Normalized form:   {-2,+,1,+,2}
-      // Denormalized form: {1,+,3,+,2}
-      //
-      // However, denormalization would use a different step expression than
-      // normalization (see getPostIncExpr), generating the wrong final
-      // expression: {-2,+,1,+,2} + {1,+,2} => {-1,+,3,+,2}
-      if (AR->isAffine() &&
-          IVUseShouldUsePostIncValue(User, OperandValToReplace, L, &DT)) {
-        const SCEV *TransformedStep =
-          TransformSubExpr(AR->getStepRecurrence(SE),
-                           User, OperandValToReplace);
-        Result = SE.getMinusSCEV(Result, TransformedStep);
-        Loops.insert(L);
-      }
-#if 0
-      // This assert is conceptually correct, but ScalarEvolution currently
-      // sometimes fails to canonicalize two equal SCEVs to exactly the same
-      // form. It's possibly a pessimization when this happens, but it isn't a
-      // correctness problem, so disable this assert for now.
-      assert(S == TransformSubExpr(Result, User, OperandValToReplace) &&
-             "SCEV normalization is not invertible!");
-#endif
-      break;
-    case Normalize:
-      // We want to normalize step expression, because otherwise we might not be
-      // able to denormalize to the original expression.
-      //
-      // Here is an example what will happen if we don't normalize step:
-      //  ORIGINAL ISE:
-      //    {(100 /u {1,+,1}<%bb16>),+,(100 /u {1,+,1}<%bb16>)}<%bb25>
-      //  NORMALIZED ISE:
-      //    {((-1 * (100 /u {1,+,1}<%bb16>)) + (100 /u {0,+,1}<%bb16>)),+,
-      //     (100 /u {0,+,1}<%bb16>)}<%bb25>
-      //  DENORMALIZED BACK ISE:
-      //    {((2 * (100 /u {1,+,1}<%bb16>)) + (-1 * (100 /u {2,+,1}<%bb16>))),+,
-      //     (100 /u {1,+,1}<%bb16>)}<%bb25>
-      //  Note that the initial value changes after normalization +
-      //  denormalization, which isn't correct.
-      if (Loops.count(L)) {
-        const SCEV *TransformedStep =
-          TransformSubExpr(AR->getStepRecurrence(SE),
-                           User, OperandValToReplace);
-        Result = SE.getMinusSCEV(Result, TransformedStep);
-      }
-#if 0
-      // See the comment on the assert above.
-      assert(S == TransformSubExpr(Result, User, OperandValToReplace) &&
-             "SCEV normalization is not invertible!");
-#endif
-      break;
-    case Denormalize:
-      // Here we want to normalize step expressions for the same reasons, as
-      // stated above.
-      if (Loops.count(L)) {
-        const SCEV *TransformedStep =
-          TransformSubExpr(AR->getStepRecurrence(SE),
-                           User, OperandValToReplace);
-        Result = SE.getAddExpr(Result, TransformedStep);
-      }
-      break;
+    break;
+  case Denormalize:
+    // Here we want to normalize step expressions for the same reasons, as
+    // stated above.
+    if (Pred(AR)) {
+      const SCEV *TransformedStep = visit(AR->getStepRecurrence(SE));
+      Result = SE.getAddExpr(Result, TransformedStep);
     }
-    return Result;
-  }
-
-  if (const SCEVNAryExpr *X = dyn_cast<SCEVNAryExpr>(S)) {
-    SmallVector<const SCEV *, 8> Operands;
-    bool Changed = false;
-    // Transform each operand.
-    for (SCEVNAryExpr::op_iterator I = X->op_begin(), E = X->op_end();
-         I != E; ++I) {
-      const SCEV *O = *I;
-      const SCEV *N = TransformSubExpr(O, User, OperandValToReplace);
-      Changed |= N != O;
-      Operands.push_back(N);
-    }
-    // If any operand actually changed, return a transformed result.
-    if (Changed)
-      switch (S->getSCEVType()) {
-      case scAddExpr: return SE.getAddExpr(Operands);
-      case scMulExpr: return SE.getMulExpr(Operands);
-      case scSMaxExpr: return SE.getSMaxExpr(Operands);
-      case scUMaxExpr: return SE.getUMaxExpr(Operands);
-      default: llvm_unreachable("Unexpected SCEVNAryExpr kind!");
-      }
-    return S;
-  }
-
-  if (const SCEVUDivExpr *X = dyn_cast<SCEVUDivExpr>(S)) {
-    const SCEV *LO = X->getLHS();
-    const SCEV *RO = X->getRHS();
-    const SCEV *LN = TransformSubExpr(LO, User, OperandValToReplace);
-    const SCEV *RN = TransformSubExpr(RO, User, OperandValToReplace);
-    if (LO != LN || RO != RN)
-      return SE.getUDivExpr(LN, RN);
-    return S;
+    break;
   }
-
-  llvm_unreachable("Unexpected SCEV kind!");
+  return Result;
 }
 
-/// Manage recursive transformation across an expression DAG. Revisiting
-/// expressions would lead to exponential recursion.
-const SCEV *PostIncTransform::
-TransformSubExpr(const SCEV *S, Instruction *User, Value *OperandValToReplace) {
-
-  if (isa<SCEVConstant>(S) || isa<SCEVUnknown>(S))
-    return S;
-
-  const SCEV *Result = Transformed.lookup(S);
-  if (Result)
-    return Result;
+const SCEV *llvm::normalizeForPostIncUse(const SCEV *S,
+                                         const PostIncLoopSet &Loops,
+                                         ScalarEvolution &SE) {
+  auto Pred = [&](const SCEVAddRecExpr *AR) {
+    return Loops.count(AR->getLoop());
+  };
+  return NormalizeDenormalizeRewriter(Normalize, Pred, SE).visit(S);
+}
 
-  Result = TransformImpl(S, User, OperandValToReplace);
-  Transformed[S] = Result;
-  return Result;
+const SCEV *llvm::normalizeForPostIncUseIf(const SCEV *S, NormalizePredTy Pred,
+                                           ScalarEvolution &SE) {
+  return NormalizeDenormalizeRewriter(Normalize, Pred, SE).visit(S);
 }
 
-/// Top level driver for transforming an expression DAG into its requested
-/// post-inc form (either "Normalized" or "Denormalized").
-const SCEV *llvm::TransformForPostIncUse(TransformKind Kind,
-                                         const SCEV *S,
-                                         Instruction *User,
-                                         Value *OperandValToReplace,
-                                         PostIncLoopSet &Loops,
-                                         ScalarEvolution &SE,
-                                         DominatorTree &DT) {
-  PostIncTransform Transform(Kind, Loops, SE, DT);
-  return Transform.TransformSubExpr(S, User, OperandValToReplace);
+const SCEV *llvm::denormalizeForPostIncUse(const SCEV *S,
+                                           const PostIncLoopSet &Loops,
+                                           ScalarEvolution &SE) {
+  auto Pred = [&](const SCEVAddRecExpr *AR) {
+    return Loops.count(AR->getLoop());
+  };
+  return NormalizeDenormalizeRewriter(Denormalize, Pred, SE).visit(S);
 }